Gradual release structures for chewing gum

ABSTRACT

Gradual release structures for the release of active agents in chewing gum and a process for making such structures are provided. The gradual release structures are formed by extrusion techniques through slot dies and comprise an active agent and a wall material.

This application is a continuation-in-part of an earlier filedapplication, Ser. No. 07/606,044, now U.S. Pat. No. 5,108,762 which is acontinuation-in-part of an earlier filed application Ser. No. 07/340,384filed Apr. 19, 1989 in the name of Joo H. Song, which issued as U.S.Pat. No. 4,978,537.

FIELD OF THE INVENTION

The invention is related to delivery systems for the gradual release ofactive agents and processes for making such systems and is particularlydirected to delivery systems for use in chewing gum that have an activeagent that is gradually released by direct interaction with a solventand extrusion processes for making such systems.

BACKGROUND OF THE INVENTION

The present invention is an advance in the art of delivery systems forthe gradual release of active agents. This invention enables an activeagent to be gradually released through the direct interaction of theagent and a solvent either within channels in the structure enclosingthe active agent or through exposure of the active agent to the solventwhen the structure enclosing the active agent is deformed.

Prior to the present invention, the gradual release of active agents,such as drugs, could be accomplished by the diffusion of the activeagent through an encapsulating material. A discussion of suchencapsulated structures is found in R. Dunn & D. Lewis, Fibrous Polymersfor the Delivery of Contraceptive Steroids to the Female ReproductiveTract, Controlled Release of Pesticides and Pharmaceuticals 125-46 (D.Lewis ed. 1981), which describes fiber-like structures. Alternatively,an encapsulating shell around the active agent could be ruptured causingexposure of the active agent to various solvents

SUMMARY OF THE INVENTION

A particular feature of this invention is to provide a gradual releasestructure having an active agent that is gradually released throughdirect interaction with a solvent. A further feature of this inventionis to provide a novel process for making such structures using meltspinning techniques.

According to the invention a chewing gum is provided which comprises agradual release structure. The gradual release structure is formed bymelt spinning a mixture of active agent and wall material, having morethan zero but less than about 55 percent by weight active agent, into afiber. If necessary, the fiber is then stretched. The fiber is cut. Aprocess for making chewing gum is further provided which comprises thesteps of preparing a gum base, preparing a water soluble bulk portion,and preparing a gradual release structure. The gradual release structureis made by preparing a mixture of active agent and wall material, havingmore than zero but less than about 55 percent by weight active agent.This mixture is melt spun into a fiber which is cut. The gradual releasestructure, the gum base, and the water soluble bulk portion arecombined.

To aid in understanding the invention one is directed towards thedrawings and the detailed description of the present preferredembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a gradual release structure in fiber form.

FIG. 1A is an illustration of the gradual release structure of FIG. 1after it has been subjected to a solvent.

FIG. 2 is a Scanning Electron Photomicrograph (SEPM) of a gradualrelease structure showing the end and side of a fiber.

FIG. 3 is a SEPM of a gradual release structure showing the side of afiber.

FIGS. 4 & 5 are SEPMs of a gradual release structure showing the ends ofa fiber and the channels within the encapsulating structure.

FIG. 6 is a SEPM showing the side and end of a fiber.

FIG. 7 is a SEPM showing the side of a fiber.

FIGS. 8 & 9 are SEPMs showing the ends of a fiber.

FIG. 10 is a graph showing the differences in sweetness over timebetween encapsulation and the gradual release structures of the presentinvention when used in chewing gums.

FIG. 11A is a SEPM of a gradual release structure extruded from a slotdie.

FIG. 11B is a SEPM of a gradual release structure extruded from a slotdie.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT OF THEINVENTION

An embodiment of a structure made in accordance with the presentinvention is a fiber having a support matrix. The support matrix is madeup of a wall material. An active agent is dispersed throughout thesupport matrix and may be in contact with itself forming a contiguousphase within the support matrix. The active agent, however, does notnecessarily have to be in a contiguous phase. The ends of the supportmatrix have openings, exposing the active agent. Additionally, theactive agent may be exposed along the sides of the fiber. This structuremay be made by stretching an already formed fiber. It is believed thatthe stretching action causes the wall material to orient itselflongitudinally. The amount of active agent in this structure is fromabout 10 percent by weight to about 55 percent by weight. It isbelieved, however, that loading as low as a fraction of a percent willexhibit gradual release characteristics. The loading of the structure isinfluenced by the characteristics of the active agent and the solubilityor extractability from the support matrix.

After the fibers are formed by melt spinning they may be stretched byapplying a draw, or stretching force, to the fibers. The draw can beapplied at a winder or by venturi after the fibers exit the die. Othermethods of stretching fibers known to the art may also be employed.

In this structure gradual release of the active agent occurs when thefiber is brought in contact with a solvent, or dispersing media, for theactive agent. The wall material is less soluble in the solvent then theactive agent and preferably the wall material should be substantiallyinsoluble in the solvent under the conditions in which the fiber isbeing used.

It is presently believed that the solvent first dissolves the activeagent in the openings at the ends of the support matrix. If the activeagent is in a contiguous phase within the support matrix, the activeagent in those openings is dissolved and spaces or channels in thesupport matrix are created. The solvent fills these channels and beginsto dissolve the newly exposed active agent, which was in contact withthe now dissolved active agent located in the openings at ends of thesupport matrix. Thus, the length of the channels in the support matrixgradually increases as the active agent directly in contact with thesolvent is dissolved.

It is presently believed that the support matrix does not prevent thedissolution of the active agent because the active agent is in acontiguous phase. Rather, the support matrix serves to limit the rate ofdissolution by restricting the area of active agent in direct contactwith the solvent to the ends of the channels within the support matrix.Thus, the solvent can gradually work its way into the fiber by followingthe contiguous phase of active agent.

Additionally, it is presently believed that depending on the stiffnessof the wall material making up the support matrix, the support matrixcan be deformed to expose new surface areas of active agent and thusbring them in direct contact with the solvent. For instance, when fibersare incorporated into chewing gum as the gum is chewed the pressure fromchewing will flatten, stretch, and deform the fibers exposing newsurface areas of active agent to the solvent. This gradual release bydeformation should occur even if the active agent is not in a contiguousphase. Higher molecular weight polymers used as wall material will notas readily exhibit this gradual release by deformation. For instance, itis believed that polyvinylacetate having a molecular weight greater thanabout 100,000 will not exhibit gradual release by deformation during gumchewing.

Furthermore, it is theorized that if the active agent is not in acontiguous phase the deformation of the support matrix may createchannels, similar to those described above, through which the solventcan be brought in contact with the active agent.

Finally, depending on the wall material chosen, the active agent chosen,and the solvent being used an extremely small amount of the active agentmay dissolve by diffusion through the wall material.

Another embodiment of a gradual release structure made in accordancewith the present invention is illustrated in FIG. 1. In this embodimentthe structure is in the form of a fiber 11 having a support matrix 12.The support matrix is made up of a wall material. An active agent 13 isdispersed throughout the support matrix and is in contact with itselfforming a contiguous phase within the support matrix. The ends 14 and 15of the support matrix have openings, exposing the active agent.Additionally, the active agent may be exposed along the sides of thefiber as can be seen in FIGS. 2 and 3. The active agent makes up atleast about 25 percent of the structure by weight.

Gradual release of the active agent in this embodiment occurs when thefiber is brought in contact with a solvent, or dispersing media, for theactive agent. The wall material is less soluble in the solvent then theactive agent and preferably the wall material should be substantiallyinsoluble in the solvent under the conditions in which the fiber isbeing used. As illustrated in FIG. 1A, the solvent first dissolves theactive agent in the openings at the ends 14 and 15 of the supportmatrix. As this material is dissolved spaces or channels 13a in thesupport matrix are opened. The solvent fills these channels and beginsto dissolve the newly exposed active agent, which was in contact withthe now dissolved active agent located in the openings at ends of thesupport matrix. Thus, the length of the channels in the support matrixgradually increase as the active agent directly in contact with thesolvent is dissolved.

It is presently believed that the support matrix does not prevent thedissolution of the active agent because the active agent is in acontiguous phase. FIG. 1 and 1A. Rather, the support matrix serves tolimit the rate of dissolution by restricting the area of active agent indirect contact with the solvent to the end of the channels within thesupport matrix. Thus, the solvent can gradually work its way into thefiber by following the contiguous phase of active agent. Additionally,depending on the wall material chosen, the active agent chosen, and thesolvent being used a small amount of the active agent may dissolve bydiffusion through the wall material. Gradual release by deformation mayalso be exhibited by this structure.

FIGS. 4 and 5 contain SEPMs of fibers made in accordance with thepresent invention. These fibers were subjected to a solvent. The spacesor channels 13a where the active agent was dissolved out are shown inthese SEPMs.

The active agent can be any material such as artificial sweeteners,powdered flavor oil, or drugs, which the gradual release of may bedesired. They must be solid or in the form of powders, including liquidsencapsulated by spray drying techniques or liquids adsorbed or absorbedinto or onto a supporting matrix, i.e., silica, zeolite, carbon black,or porous matrices. Combinations of different active agents in the samestructure may also be employed. For purposes of illustration, possibleactive agents may be: high intensity sweeteners, such as Aspartame,Alitame, Acesulfame-k and its salts, saccharin and its salts, Thaumatin,Sucralose, Cyclamic acid and its salts, Monellin, and Dihydrochalcones;acidulants, such as malic acid, citric acid, tartaric acid, and fumaricacid; salt, such as sodium chloride and potassium chloride; bases, suchas, magnesium hydroxide and urea; flavors, such as spray dried naturalor synthetic adsorbed onto silica, and absorbed into maltodextrin;flavor modifiers, such as Thaumatin; breath fresheners, such as zincchloride, encapsulated menthol, encapsulated anise, zinc glucinate, andencapsulated chlorophyll; glycyrrhizins, including glycyrrhizic acid orsalts (food grade) thereof, one such commercially available compoundcalled Magnasweet 135 is manufactured by MacAndrew and Forbes, Camden,N.J., these compounds may be combined with a sugar; and medicaments.

Of the various types of high intensity sweeteners, glycyrrhizins, suchas Magnasweet 135, show surprisingly good results when combined withwall such as PVAc. When using Magnasweet 135, the occurrence of "offnotes" (a residual taste of licorice) can be avoided by combining theproduct with a sugar. Furthermore, Magnasweet 135 can be used to form agradual release structure, by combining it with a wall material such asPVAc and a sugar and heating the mixture in the temperature range of140°-160° C. The resulting material can then be ground and exhibitsgradual release characteristics.

Care must be taken to avoid the degradation of the active agent fromhigh temperatures, shear, or other conditions, which may occur duringformation. The wall material can be any spinnable synthetic or naturepolymer such as polyethylene, polyvinylacetate, polyesters, chitosan,and copolymers and polymer blends of these polymers. The active agentand wall material must meet the solubility requirements discussed above.Additionally, they must be immiscible with each other and capable ofbeing uniformly dispersed when mixed together during the melt spinningprocedure.

The gradual release structures of the present invention can be used inchewing gum. Chewing gum consists of a gum base to which a water solublebulk portion may normally be added.

Chewing gum bases generally comprise a combination of elastomers andresins together with plasticizers and inorganic fillers.

The gum base may contain natural gums and/or synthetic elastomers andresins. Natural gums include both elastomers and resins. Suitablenatural gums include, but are not limited to chicle, jellutong, sorva,nispero tunu, niger gutta, massaranduba belata, and chiquibul.

When no natural gums are used, the gum base is referred to as"synthetic" and the natural gums are replaced with synthetic elastomersand resins. Synthetic elastomers may include polyisoprene,polyisobutylene, isobutylene-isoprene copolymer, styrene butadienerubber, a copolymer form Exxon Corp. under the designation "butylrubber," and the like.

The amount of elastomer used in the gum base can typically be variedbetween about 10 and about 20 percent depending on the specificelastomer selected and on the physical properties desired in the finalgum base. For example, the viscosity, softening point, and elasticitycan be varied.

Resins used in gum bases may include polyvinylacetate, polyethylene,ester gums, (resin esters of glycerol), polyvinylacetate polyethylenecopolymers, polyvinylacetate polyvinyl laureate copolymers, andpolyterpenes. Additionally, a polyvinylacetate obtained from Monsantounder the designation "Gelva" and a polyterpene obtained from Herculesunder the designation "Piccolyte" may be used.

As with the elastomer, the amount of resin used in the gum base can bevaried depending on the particular resin selected and on the physicalproperties desired in the final gum base.

Preferably, the gum base also includes plasticizers selected from thegroup consisting of fats, oils, waxes, and mixtures thereof. The fatsand oils can include tallow, hydrogenated and partially hydrogenatedvegetable oils, and cocoa butter. Commonly employed waxes includeparaffin, microcrystalline and natural waxes such as beeswax andcarnauba. Additionally, mixtures of the plasticizers may be used such asa mixture of paraffin wax, partially hydrogenated vegetable oil, andglycerol monostearate.

Preferably, the gum base also includes a filler component. The fillercomponent is preferably selected from the group consisting of calciumcarbonate, magnesium carbonate, talc, dicalcium phosphate and the like.The filler may constitute between about 5 to about 60 percent by weightof the gum base. Preferably, the filler comprises about 5 to about 50percent by weight of the gum base.

Further, gum bases may also contain optional ingredients such asantioxidants, colors, and emulsifiers.

These ingredients of the gum base can be combined in a conventionalmanner. In particular, the elastomer, resins, plasticizers, and thefiller are typically softened by heating and then mixed for a timesufficient to insure a homogenous mass. The mass can be formed intoslabs, or pellets and allowed to cool before use in making chewing gum.Alternatively, the molten mass can be used directly in a chewing gummaking process.

Typically, the gum base constitutes between about 5 to about 95 percentby weight of the gum. More preferably the insoluble gum base comprisesbetween 10 and 50 percent by weight of the gum and most preferably about20 to about 35 percent by weight of the gum.

In general, a chewing gum composition typically comprises a watersoluble bulk portion added to the water insoluble chewable gum baseportion. The flavoring agents are typically water insoluble. The watersoluble portion dissipates with a portion of the flavoring agent over aperiod of time during chewing, while the gum base portion is retained inthe mouth throughout the chew.

The water soluble portion of the chewing gum may further comprisesofteners, sweeteners, flavoring agents and combinations thereof.Softeners are added to the chewing gum in order to optimize thechewability and mouth feel of the gum. Softeners, also known in the artas plasticizers or plasticizing agents, generally constitute betweenabout 0.5 to about 15.0 percent by weight of the chewing gum. Softenerscontemplated by the present invention include glycerin, lecithin, andcombinations thereof. Further, aqueous sweetener solutions such as thosecontaining sorbitol, hydrogenated starch hydrolysates, corn syrup andcombinations thereof may be used as softeners and binding agents in thechewing gum.

Sugar sweeteners generally include saccharide containing componentscommonly known in the chewing gum art which comprise but are not limitedto sucrose, dextrose, maltose, dextrin, dried invert sugar, fructose,levulose, galactose, corn syrup solids, and the like, alone or in anycombination. Nonsugar sweeteners can include sorbitol, mannitol, andxylitol.

Optional ingredients such as colors, emulsifiers and pharmaceuticalagents may be added to the chewing gum.

In general, chewing gum is manufactured by sequentially adding thevarious chewing gum ingredients to a commercially available mixer knownin the art. After the ingredients have been thoroughly mixed, the gummass is discharged from the mixer and shaped into the desired form suchas by rolling into sheets and cutting into sticks, extruding into chunksor casting into pellets.

Generally, the ingredients are mixed by first melting the gum base andadding it to the running mixer. The base may also be melted in the mixeritself. Color or emulsifiers may also be added at this time. A softenersuch as glycerin may also be added at this time along with syrup and aportion of bulking agent. Further portions of the bulking agent may thenbe added to the mixer. The flavoring agent is typically added with thefinal portion of the bulking agent.

The entire mixing procedure typically takes about fifteen minutes, butlonger mixing times may sometimes be required. Those skilled in the artwill recognize that many variations of the above described procedure maybe followed.

Gradual release structures that embody the present invention are made bymelt spinning a uniform mixture of active agent and wall material into afiber. The general principles for melt spinning polymers are well knownin the art and are described in F. Billmeyer, Jr., Text Book of PolymerScience. 518-22 (Wiley International Edition, 2nd), which isincorporated herein by reference. In this process a mixture of a polymerfor the wall material and an active agent are prepared in powder orpellet form. The particles of polymer and active agent are mixedtogether into a homogeneous phase. The concentration of active agent inthis mixture is such that the particles of active agent may be incontact with each other. The mixture is melt spun to produce fibers.These fibers are then gently broken into smaller sizes. Any grindingmachine or knife which reduces the length of fiber without excessivelydamaging the support matrix is suitable. Fiber brittleness eases thecutting process of the fiber and can be achieved by concentrating thesolid active agent particles. To avoid the detection of the fibers whenchewing the gum, fibers of a size such that they can pass through a 60mesh screen are used.

The fact that a polymer or polymer blend initially shows an unacceptablyhigh pressure for extrusion, does not automatically eliminate thepossibility of using it in this process. Processability often can beimproved by increasing the processing temperature, introducingplasticizers, changing nozzle dimensions, adding dispersing agents, ormodifying it by blending with other polymers. Changing nozzle dimensionssuch as by increasing the nozzle size can result, for example, ingreater throughput, lower residence time, and lower pressure and sheer.Additionally, increasing the size of the nozzle results in an extrudatethat is easier to handle and easier to cool. By way of illustrationlarger fibers can be extruded using a slot die having a 1 inch by 1/8inch opening. Handling and storage of the ground particles can also befacilitated by coating or blending them with a fumed silica, such asCab-O-Sil. Fibers of this type have been made having the followingcompositions (percentages are given by weight):

(1) 75% PVAc having a molecular weight of about 50,000-80,000 as thewall material and 25% Acesulfame-k as the active agent;

(2) 47.26% PVAc having a molecular weight of about 30,000 and 37.81%PVAc having a molecular weight of about 15,000 as the wall material and37.81% sucrose, 9.45% Magnasweet 135, and 0.50% Magnesium Stearate asthe active agent;

(3) 75% PVAc having a molecular weight of about 50,000-80,000 as thewall material and 25% finely ground salt as the active agent;

(4) 75% PVAc having a molecular weight of about 30,000 as the wallmaterial and 25% Acesulfame-k as the active agent;

(5) 74.6% PVAc having a molecular weight of about 50,000-80,000 as thewall material and 13.8% Magnasweet 135, 11.1% finely ground salt, and0.5% Magnesium Stearate as the active agent;

(6) 75% PVAc having a molecular weight of about 50,000-80,000 as thewall material and 15% Magnasweet 135 and 10% sugar as the active agent;

(7) 99.5% (a mixture of 74.6% PVAc having a molecular weight of about50,000-80,000 as the wall material and 13.8% Magnasweet 135, 11.1%finely ground salt, and 0.5% Magnesium Stearate as the active agent) and0.5% fumed silica; and,

(8) 99.5% (a mixture of 75% PVAc having a molecular weight of about50,000-80,000 as the wall material and 15% Magnasweet 135 and 10% sugaras the active agent) and 0.5% fumed silica.

By way of example, this process was carried out on the following typesof equipment.

Model 1125 Instron Capillary Rheometer

A Model 1125 Instron Capillary Rheometer, with capillary hole diameterof 152 microns was used to extrude fibers. The barrel diameter was 3/8inches. The die had a Length to diameter ratio of 0.083 and had 1 hole.In this application of the process L-aspartyl-L-phenylalanine methylester (Aspartame) was used as the active agent. A polyvinylacetate(PVAc) having a molecular weight from about 50,000 to 80,000 was chosenas the wall material.

This laboratory scale Capillary Rheometer could not provide enoughmixing action during extrusion. Thus, prior to extrusion, samples werepreblended by two methods. In one method, PVAc was dissolved inMethylene Chloride (CH₂ Cl₂) at room temperature, and then Aspartame wasmixed into this solution. The solvent was evaporated overnight undervacuum at 60° C. to form a solid material. This material was ground to apowder to facilitate addition into the rheometer.

This method is indicated in Table 1 as "Solution Blended." In the othermethod, samples were prepared for extrusion by directly blending theAspartame with a polymer melt of the wall material in a heated beaker at140° C. The blend was dried under vacuum at 60° C. for about 5 hours toremove water. This method is indicated in Table 1 as "Melt Blended."

Using these two methods of mixing the wall material and the activeagent, fibers with varying amounts of Aspartame were produced. Theparameters used for those examples are set out in the following Table 1.The Jet Speed is the speed of the material being meltspun in thecapillary.

                  TABLE 1                                                         ______________________________________                                        Extrusion     Jet Speed                                                       (kgf)         Temp.     (m/min)  Load                                         ______________________________________                                        Example 1)                                                                    Aspartame     140° C.                                                                           5       13                                           17 wt. %                10       18                                           in PVAc                 20       32                                           (Solution Blended)      50       57                                                                   100      76                                           Example 2)                                                                    Aspartame     150° C.                                                                           5       18                                           17 wt. %                10       23                                           in PVAc                 20       34                                           (Solution Blended)      50       51                                                                   100      68                                           Example 3)                                                                    Aspartame     140° C.                                                                           5       41-59                                        17 wt. %                10       23-68                                        in PVAc                 20        45-113                                      (Melt Blended)          50       68                                           Example 4)                                                                    Aspartame     140° C.                                                                           5       13                                           29 wt. %                10       16                                           in PVAc                 20       20                                           (Solution Blended)      100      52                                           Example 5)                                                                    Aspartame     150° C.                                                                           5        9                                           29 wt. %                10       13                                           in PVAc                 20       17                                           (Solution Blended)      50       25                                                                   100      36                                                                   200      50                                                                   500      59                                           Example 6)                                                                    Aspartame     140° C.                                                                           5       32                                           29 wt. %                10       45                                           in PVAc                 20        90-180                                      (Melt Blended)          50       less than                                                                     180                                          Example 7)                                                                    Aspartame     140° C.                                                                           5       14                                           35 wt. %                10       17                                           in PVAc                 20       25                                           (Solution Blended)      50       36                                           Example 8)                                                                    Aspartame     140° C.                                                                           5       10                                           35 wt. %                10       12                                           in PVAc                 20       18                                           (Solution Blended)      50       27                                                                   100      41                                                                   200      55                                           Example 9)                                                                    Aspartame     140° C.                                                                           5       36-41                                        35 wt. %                10       54-64                                        in PVAc                 20       113-136                                      (Melt Blended)          50       272-363                                      ______________________________________                                    

Table 1, shows that the spinnability of PVAc blends was good and nothighly dependent on the Aspartame loading level. The extrudates ofPVAc/Aspartame blends shown in Table 1 were brittle at 17% Aspartameloading. Brittleness increased as the Aspartame loading level increased.The diameter of the extruded fibers due to die swell was slightly largerthan the capillary, which was 152 microns.

The extruded fibers were gently ground with a mortar and pestle. Thediameter to length ratio of these ground fibers was narrowly distributedwith no major breakage of fibers along the longitudinal direction.

FIGS. 2 through 5 are SEPMs of fibers having 29% by weight Aspartame inPVAc that were prepared by the solution blending technique describedabove and extruded at 150° C. FIGS. 6 through 9 are SEPMs of fibershaving 17% by weight Aspartame in PVAc that were prepared by the meltblending technique described above and extruded at 140° C. Both sampleswere extracted with water as the solvent for four hours. The spacesshown in the SEPMs are places from which Aspartame was dissolved. FIGS.8 and 9 show that at 17% loading, the solid particles of Aspartame areisolated in polymer. Thus, Aspartame could not completely dissolve outinto the water without further physical breaking of the polymericstructure. At 29% loading, FIGS. 4 and 5, however, the solid particlesof Aspartame formed a contiguous phase as illustrated in FIG. 1. Thus,channels in the encapsulating structure were opened and the Aspartamewas gradually released, until virtually none remained.

This result is demonstrated by chew out data given in Table 2. Chewinggums having a formulation of:

    ______________________________________                                        Ingredient       % by weight                                                  ______________________________________                                        Sorbitol         49.5                                                         Stick Gum Base   25.5                                                         Syrup            9.1                                                          Mannitol         8.0                                                          Glycerine        6.3                                                          Lecithin         0.2                                                          Flavor (Peppermint)                                                                            1.4                                                          ______________________________________                                    

were prepared with fibers having 17% loading and 29% loading. The syrupin the gum consisted of 67% by weight Lycasin solids, 5.36% by weightwater, and 27.14% by eight glycerin. A control gum was prepared usingthe above formulation with the addition of free Aspartame instead of thefibers. The gums were then chewed by five volunteers. Gum cuds werecollected at different chewing times and Aspartame concentration wasanalyzed by High Performance Liquid Chromatography.

                  TABLE 2                                                         ______________________________________                                        Type of fiber                                                                              % Aspartame in Gum After:                                        used in gum  0 min.    5 min.  10 min. 20 min.                                ______________________________________                                        Control      0.18      0.11    0.06    0.02                                   Aspartame/PVAc                                                                             0.11      0.10    0.11    0.10                                   17% by wt.                                                                    Aspartame/PVAc                                                                             0.18      0.15    0.14    0.12                                   29% by wt.                                                                    ______________________________________                                    

The control gums contain free Aspartame. The PVAc/Aspartame gums (17% bywt. Aspartame) contained fibers of the type shown in FIGS. 6 through 9.The PVAc/Aspartame gums (29% by wt. Aspartame) contained fibers of thetype shown in FIGS. 2 through 5. As shown in Table 2 the release rate ofAspartame from the fiber loaded at 17% was much slower than the releaserate from the fiber loaded at 29%. The release rate of Aspartame fromthe fiber loaded at 29% is significantly slower than the control, butfaster than the 17% sample.

Liquid Chromatography analysis was carried out on the fibers spun at140° C. and at 150° C. in examples 1 through 9 to determine the amountof thermal degradation of Aspartame occurring during the melt spinningprocess discussed above. At 140° C. thermal degradation of Aspartame isless than 10%. At 150° C. the percent thermal degradation of Aspartameapproached 20%.

The residence time of Aspartame/polymer blend in the Capillary Rheometerused to prepare the above samples was about twenty minutes. Inproduction scale spinning, residence time could be reduced to around 20seconds to two minutes. This would greatly reduce the degree ofAspartame degradation. At 90°-100° C. using a twin screw extruder at 2minutes residence time, no degradation is observed.

Twin Screw Extruder

In Examples 10-23 a type LSM 30:34 twin screw extruder from AmericanLeistritz Extruder Corporation was used to produce the fibers.Generally, a homogeneous mixture of wall material and active agent inpowdered form were poured into a hopper on the extruder. The hopper feedscrews which forced the mixture through heated sections of the extruder,melting the polymer, and then through a die. The die consists of aplurality of holes having a specific diameter and length. Upon leavingthe die the fibers were stretched by either drawing them with a winderor by blowing air past them with a venturi.

The twin screw extruder consisted of two sets of eight element screws.These screws can operate in an intermeshing fashion in either aco-rotational or a counter rotational mode. These screws can function askneading elements or conveying elements. For the following examples fourkneading elements alternating with four conveying elements were used.Other configurations are possible and will depend on the processconditions and the types of materials being melt spun and the degree ofmixing required.

The twin screw extruder used in the following examples was divided intoeight zones. The temperature of each zone was controlled. For example, amixture of 50 percent by weight PVAc with a molecular weight of about30,000, 25 percent by weight PVAc with a molecular weight of about15,000, and 25 percent by Aspartame was melt spun to produce fibers.Operating the extruder with a 1 mm die having 5 holes at 30 rpm,resulted in the production of 5 pounds of fiber per hour. The followingtemperatures in degrees centigrade were used for each zone:

    ______________________________________                                        Zone               Temp.                                                      ______________________________________                                        Feeding or hopper zone                                                                           85                                                         2                  95                                                         3                  95                                                         4                  95                                                         5                  95                                                         6                  95                                                         7                  95                                                         Die or last zone   102                                                        ______________________________________                                    

Operating the extruder with a 1 mm die having 5 holes at 333 rpm,resulted in the production of 50 pounds of fiber per hour. The followingtemperatures in degrees centigrade were used for each zone:

    ______________________________________                                        Zone               Temp.                                                      ______________________________________                                        Feeding or hopper zone                                                                           85                                                         2                  97                                                         3                  97                                                         4                  97                                                         5                  97                                                         6                  97                                                         7                  97                                                         Die or last zone   102                                                        ______________________________________                                    

In the following examples dies having a diameter of 1 mm and 0.3 mm wereused. The 1 mm die had 5 holes and had a diameter to length ratio ofabout 4. The 0.3 mm die had 34 holes and had a diameter to length ratioof 2.3. The temperatures set out in these examples were taken from anaverage of all heating zones on the extruder.

EXAMPLE 10

Using a 1 mm die, fibers having 10% by weight Acesulfame-k (a highintensity sweetener purchased from Hoecht, of W. Germany) as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extruded at 110°-115° C. The fibers were drawn bya winder and had a thickness of 0.2-0.3 mm. The Acesulfame-k particlesdispersed very well in the fibers and the fibers exhibited a gradualrelease of the active agent when chewed alone.

EXAMPLE 11

Using a 1 mm die, fibers having 25% by weight Acesulfame-k as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extended at 110° C. The fibers were drawn by awinder. The fibers were between 0.3-0.4 mm in thickness. TheAcesulfame-k particles dispersed very well in the fibers and the fibersexhibited a gradual release of the active agent when chewed alone.

EXAMPLE 12

Using a 1 mm die, fibers having 10% by weight Aspartame as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extended at 100° C. The fibers were drawn by awinder and had a thickness of 0.2-0.3 mm. The Aspartame dispersed verywell in the fibers and the fibers exhibited a gradual release of theactive agent when chewed alone.

EXAMPLE 13

Using a 1 mm die, fibers having 10% by weight Aspartame as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extruded at 100° C. The fibers were drawn by thewinder and had a thickness of about 0.2 mm. The Aspartame dispersed verywell in the fibers and the fibers exhibited an excellent gradual releaseof the active agent when chewed alone.

EXAMPLE 14

Using a 1 mm die, fibers having 35% by weight Sodium Saccharin as theactive agent and having PVAc with a molecular weight of about50,000-80,000 as the wall material were extruded at 100° C. The fiberswere drawn at the winder and were 0.4-0.5 mm thick. The Sodium Saccharindispersed very well in the fibers, although the fibers were softer thanthose of examples 10-13. The fibers exhibited a gradual release of theactive agent when chewed alone.

EXAMPLE 15

Using a 1 mm die, fibers having 35% by weight Saccharin Acid as theactive agent and having PVAc with a molecular weight of about50,000-80,000 as the wall material were extruded at 100° C. The fiberswere drawn at the winder and were 0.4-0.5 mm thick. The Saccharin Aciddispersed very well in the fiber, although the fibers were softer thanthose of examples 10-13. The fibers exhibited a gradual release of theactive agent when chewed alone.

EXAMPLE 16

Using a 1 mm die, fibers having 6.13% by weight NaCl, 3.87% by weightKCl as the active agents and having PVAc with a molecular weight ofabout 30,000 as the wall material were extruded at 113° C. The fiberswere drawn at the winder and were 0.12 mm in thickness. The NaCl and KClparticles were dispersed in the fiber. The fibers exhibited good gradualrelease of the active agent when chewed alone.

EXAMPLE 17

Using a 1 mm die, fibers having 6.13% by weight NaCl, 3.87% by weightKCl as the active agents and having PVAc with a molecular weight ofabout 15,000 as the wall material were extruded at 90° C. The fiberswere drawn by air blowing and were 0.12 mm in thickness and wereslightly weaker than the fibers of Example 16. The fibers exhibited agradual release of the active agent when chewed alone.

EXAMPLE 18

Using a 1 mm die, fibers having 24.52% by weight Na Cl, and 15.48% KClby weight as the active agents and having Allied Chemical PE 735 as thewall material were extruded at 85°-90° C. The fibers were 0.96 mm thickand were drawn by air blowing. The fibers exhibited gradual release ofsalts.

EXAMPLE 19

Using a 1 mm die, fibers having 25% by weight Diamonium Phosphate as theactive agent and having PVAc with a molecular weight of about50,000-80,000 as the wall material were extruded at 100° C. The fiberswere drawn by air blowing and had a thickness of 0.20-0.38 mm.

EXAMPLE 20

Using a 1 mm die, fibers having 25% by weight NaF as the active agentand having PVAc with a molecular weight of 50,000-80,000 were extrudedat 90°-100° C. The fibers were drawn by air blowing and had a thicknessof 0.18-0.25 mm.

EXAMPLE 21

Using a 1 mm die, fibers having 25% by weight Mg (OH)₂ as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extruded at 90°-100° C. The fibers were drawn byair blowing and had a thickness of 0.25 mm.

EXAMPLE 22

Using a 1 mm die, fibers having 25% by weight Acesulfame-k as the activeagent and having PVAc with a molecular weight of about 30,000 as thewall material were extruded at 90°-100° C. The fibers were drawn by airblowing and had a thickness of 0.13 mm. The fiber exhibited the bestrelease characteristics of the examples.

EXAMPLE 23

Using a 0.3 mm die, fibers having 25% by weight Aspartame as the activeagent and having PVAc with a molecular weight of about 50,000-80,000 asthe wall material were extruded at 90°-100° C. In making the fibers ofthis example prior to extrusion the PVAc and Aspartame were premixed inmethylene chloride, following the solution blended method describedabove. The fibers were drawn by a winder and had a thickness of 0.127mm.

In the following examples, dies having a diameter of 2 mm and 6 holeswere used. The dies had a diameter to length ratio of about 1 to 5. Thetemperatures set out in these examples were taken from the range of allheating zones on the extruder.

EXAMPLE 24

Using a 2 mm die fibers having 10% Magnasweet 135 by weight and 40%sugar by weight as the active agents and having 50% PVAc with amolecular weight of about 30,000 as the wall material were extruded atabout 80° to 100° C.

EXAMPLE 25

Using a 2 mm die fibers having 9% Magnasweet 135 by weight and 36% sugarby weight as the active agents and having 45% PVAc with a molecularweight of about 30,000 and 10% PVAc with a molecular weight of about50,000-80,000 as the wall materials were extruded at about 90°-100° C.

EXAMPLE 26

Using a 2 mm die fibers having 10% Magnasweet 135 by weight and 30%sugar by weight as the active agents and having 40% PVAc with amolecular weight of about 50,000-80,000 as the wall materials wereextruded at about 90°-100° C.

EXAMPLE 27

Using a 2 mm die fibers having 10% Magnasweet 135 by weight and 30%sugar by weight as the active agents and having 60% PVAc with amolecular weight of about 30,000 as the wall material were extruded atabout 90°-100° C.

EXAMPLE 28

Using a 2 mm die fibers having 10% Magnasweet 135 by weight and 20%sugar by weight as the active agents and having 70% PVAc with amolecular weight of about 50,000-80,000 as the wall materials wereextruded at about 90°-100° C.

EXAMPLE 29

Using slotted 1 inch by 11/4 inch die instead of a 2 mm die fibershaving 9.5% Magnasweet 135 by weight and 38% sugar by weight as theactive agents and having 47.5% PVAc with a molecular weight of about30,000 and 5% PVAc with a molecular weight of about 50,000 to 80,000 asthe wall materials were extruded at about 80°-100° C.

Gradual release fibers having the same formulation as those of example18 (24.52% NaCl and 15.48% KCl as active agents and PE 735 as the wallmaterial) were incorporated into gum having the following formulation:

    ______________________________________                                        Ingredient        % by weight                                                 ______________________________________                                        Sugar             54.9                                                        Stick Base        19.3                                                        Corn Syrup        16.8                                                        Dextrose Monohydrate                                                                            7.3                                                         Glycerin          0.65                                                        Fruit Flavor      0.8                                                         Fibers            0.25                                                        ______________________________________                                    

This gum was chewed by a panel of sensory experts who found that the gumwas sweeter in the intermediate chew in addition to longer lastingflavor than a control gum of similar formulation which did not containgradual release fibers.

Similarly, gradual release fibers made in accordance with the presentinvention were incorporated into a gum having the following ingredients:

    ______________________________________                                        Ingredient     % by weight                                                    ______________________________________                                        Stick Base     25.5                                                           Sorbitol       44.7                                                           Mannitol       8.0                                                            Syrup          9.1                                                            Glycerin       6.3                                                            Lecithin       0.2                                                            Brown Color    0.05                                                           Mint Flavor    1.4                                                            Water          4.05                                                           Fibers         0.7                                                            ______________________________________                                    

The syrup consisted of 67% by weight Lycasin solids, 5.36% by weightwater, and 27.14% by weight glycerin. The active agent in the gradualrelease fibers was Aspartame loaded at 33% by weight.

This gum was chewed by a panel of sensory experts and found to havesuperior sweetness lasting when compared to a control gum of similarformulation that did not contain gradual release fibers.

Chewing gums were prepared having the following general formula:

    ______________________________________                                        Ingredient      % by weight                                                   ______________________________________                                        Sugar           50.76                                                         Base            20.68                                                         Corn Syrup      16.86                                                         Dextrose        10.15                                                         Glycerin        0.94                                                          Spearmint Flavor                                                                              0.56                                                          Brown Color     0.05                                                          ______________________________________                                    

To three gums having the above formula 0.3% by weight Aspartame wasadded. In the first gum, the Aspartame was contained in gradual releasefibers having 25% by weight loading of Aspartame and a wall materialconsisting of PVAc having a molecular weight of about 15,000. In thesecond gum, the Aspartame was contained in gradual release fibers having25% by weight loading of Aspartame and a wall material consisting of 50%(by weight of the total fiber) PVAc having a molecular weight of about30,000 and 25% (by weight of the total fiber) PVAc having a molecularweight of about 100,000. In the third gum the Aspartame was encapsulatedby the encapsulation methods disclosed in U.S. patent application Ser.No. 134,948, filed Dec. 18, 1987. A fourth gum of the above formula wasprepared to which no Aspartame was added.

Ten expert panelists were asked to chew samples of the above four gumsand rate the sweetness of each gum over a 20-minute period. Sweetnessratings were taken after the first half minute of chewing, the firstfull minute of chewing and each full minute thereafter. This data isdepicted graphically in FIG. 10. Analysis of this data shows thatchewing gums containing gradual release structures exhibitedsignificantly improved sweetness in the final chew when compared to theother two gums. Particularly, the sweetness levels in the gum containingthe gradual release structures began to increase after 9 minutes ofchewing while the other gums' sweetness was declining. Accordingly, agum containing both encapsulated sweeteners and gradual releasesweeteners could be made to obtain the benefits of both delivery systemsin the same gum. The encapsulated sweetener providing sweetness duringthe initial and intermediate part of the chew and the gradual releasestructure providing sweetness during the final chew. Additionally, thedata in FIG. 10 illustrates the difference in release rate betweenfibers having different wall material.

Gradual release fibers having a formulation of 47.26% PVAc having amolecular weight of about 30,000 and 4.98% PVAc having a molecularweight of about 15,000 as the wall materials and 37.81% sugar, 9.45%Magnasweet 135, and 0.5% Magnesium Stearate as the active agents weremade. The Magnasweet 135 was first mixed with the Magnesium Stearate.The rest of the components were then added to this mixture. The fiberswere extruded using a slot die of 1 inch by 1/16 inch. The fibers werestretched by venturi. The temperature zones during extrusion werebetween 90° and 100° C. The temperature was 950° C. at the die. Thesefibers were incorporated into a gum having the following formulation:

    ______________________________________                                        Ingredient        % by weight                                                 ______________________________________                                        Sugar             53.3                                                        Stick Base        24.0                                                        Corn Syrup        5.1                                                         Dextrose Monohydrate                                                                            13.4                                                        Glycerin          2.0                                                         Flavor (Mint)     1.4                                                         10% Salt Solution 0.1                                                         Fibers            0.7                                                         ______________________________________                                    

This gum was chewed by about 100 people in a blind taste test. Thecontrol gum had the same formulation but had no fibers and noMagnasweet. The test showed that in comparison to the control: the gumhaving the fibers was preferred overall; that it had better flavor; thatit had longer lasting taste, including sweetness; and that it had asweeter taste.

Many variations of the invention suggest themselves to those skilled inthe art in view of the above disclosure without departing from thespirit and scope of this invention.

I claim:
 1. A chewing gum which comprises:a gum base; a water solublebulk portion; and, a gradual release structure formed by extruding amixture of active agent and polymeric wall material having more thanzero but less than about 55 percent by weight active agent through aslot die, into a fiber, and cutting the fiber.
 2. The chewing gum ofclaim 1 in which the wall material comprises a polyvinylacetate.
 3. Thechewing gum of claim 1 in which the active agent comprises Aspartame. 4.The chewing gum of claim 1 in which the wall material comprisespolyvinylacetate having a molecular weight of about 15,000.
 5. Thechewing gum of claim 1 in which the wall material comprisespolyvinylacetate having a molecular weight of about 30,000.
 6. Thechewing gum of claim 1 in which the wall material comprisespolyvinylacetate having a molecular weight from about 50,000 to about80,000.
 7. The chewing gum of claim 1 in which the wall materialcomprises a blend of polyvinylacetates having molecular weights fromabout 15,000 to about 80,000.
 8. The chewing gum of claim 1 in which thegradual release structure can pass through a 60 mesh screen.
 9. Thechewing gum of claim 1 in which the active agent comprises a highintensity sweetener.
 10. The chewing gum of claim 1 in which the activeagent comprises Alitame.
 11. The chewing gum of claim 1 in which theactive agent comprises Acesulfame-k.
 12. The chewing gum of claim 1 inwhich the high intensity sweetener comprises a glycyrrhizin.
 13. Thechewing gum of claim in which the active agent comprises a sugar and aglycyrrhizin.
 14. A process for making chewing gum which comprises thesteps of:a. preparing a gum base; b. preparing a water soluble bulkportion; c. preparing a gradual release structure which comprises thesteps of:i. preparing a mixture of active agent and wall material,having more than zero but less than about 55 percent by weight activeagent; ii. extruding the mixture into a fiber through a slot die; and,iii. cutting the fiber; and, d. combining the gradual release structure,the gum base and the water soluble bulk portion.
 15. The process ofclaim 14 in which the active agent comprises Aspartame.
 16. The processof claim 14 in which the wall material comprises polyvinylacetate havinga molecular weight of about 15,000.
 17. The process of claim 14 in whichthe wall material comprises polyvinylacetate having a molecular weightof about 30,000.
 18. The process of claim 14 in which the wall materialcomprises polyvinylacetate having a molecular weight from about 50,000to about 80,000.
 19. The process of claim 14 in which the gradualrelease structure can pass through a 60 mesh screen.
 20. The process ofclaim 14 in which the wall material comprises a blend ofpolyvinylacetates having molecular weights from about 15,000 to about80,000.
 21. The process of claim 14 in which the active agent comprisesa high intensity sweetener.
 22. The process of claim 14 in which theactive agent comprises Alitame.
 23. The process of claim 14 in which theactive agent comprises Acesulfame-k.
 24. The process of claim 14 inwhich the high intensity sweetener comprises a glycyrrhizin.
 25. Theprocess of claim 14 in which the active agent comprises a sugar and aglycyrrhizin.
 26. A process for making a chewing gum having a gradualrelease structure which comprises the steps of:preparing a gum base;preparing a water soluble bulk portion; preparing a mixture ofglycyrrhizin and wall material, having from about 10 percent by weightglycyrrhizin; extruding the mixture through a slot die to form a fiber;cutting the fiber; and, combining the gum base, water soluble bulkportion and gradual release structure.
 27. The process of claim 26 inwhich the wall material comprises polyvinylacetate having a molecularweight of about 15,000.
 28. The process of claim 26 in which the wallmaterial comprises polyvinylacetate having a molecular weight of about30,000.
 29. The process of claim 26 in which the wall material comprisespolyvinylacetate having a molecular weight from about 50,000 to about80,000.
 30. The process of claim 26 in which the wall material comprisesa blend of polyvinylacetates having molecular weights from about 15,000to about 80,000.
 31. The process of claim 26 in which the gradualrelease structure can pass through a 60 mesh screen.
 32. The process ofclaim 26 in which the sugar is mixed with the mixture of glycyrrhizinand wall material.